Treatment of nylon filaments



J B. w. BEDELL 2,889,611

' TREATMENT OF NYLON FILAMENTS Filed Sept 24. 1954 ZJYIZJYZVJE Banner Inl- 5:24-11.

effects in the use of the material.

States TREATMENT OF NYLUN FILAMENTS Berkley W. Bedell, Spirit Lake, Iowa Application September 24, 1954, Serial No. 458,064

2 Claims. (Cl. 2876) i ate t into a quenching bath. The filament produced by this method is tough and strong and has a high gloss at the surface thereof. Such filaments, and particularly monofilaments, produced from the nylon thermoplastic material, are sometimes so glossy as to produce undesirable This invention is not concerned with the ornamental appearance of a shiny filamentor of textile material produced therefrom as opposed to a dull filament and its characteristic textile product, but rather is concerned with functional aspects of the filament when actively used to perform such type of special operation where the physical quality of the surface of the line comes into play as well as the usual qualities of nylon filaments, such as its strength and flexibility. In some instances it has been recognized that it would be desirable to roughen the surface of monofilament nylon, and prior art practice has suggested the physical abrasion of the surface to scratch, dull and otherwise roughen the surface and to eliminate the hard glossy surface characteristic of monofilament extrusions. In addition to being laborious and unreliable, such physical abrasion substantially weakens a given diameter of monofilament while still not achieving the characteristic desired by the roughening process.

Although this invention contemplates the treatment of the outer surface of nylon filaments for any suitable purpose where reliable results can be achieved without As my first example, monofilament lines are becoming A more and more common in fishing and are used particularly frequently in casting with spinning reels. Fishermen recognize the desirability of the monofilament nylon lines due to their high strength and flexibility. The ease of casting is important especially where light weight lures are employed. Further, the monofilament nylon line has a translucent quality which tends to blend the line into the background when used in and on the water, and therefore can serve without frightening or warning fish while the user is angling. Unfortunately, however, the high gloss characteristic of this type of filament tends to reflect concentrated rays of light during sunny weather and the natural translucence of the material is often more than nullified by light reflectivity which easily catches the eye of fish and thereby makes them wary and suspicious.

As my second example of use and application of my invention in a widely divergent field, I refer to the use of nylon filaments for brushes designed to retain viscous liquids such as paint. Here again the natural shiny nylon "ice bristles tend to encourage the flow and release of paint and the like and, although otherwise ideal, force the painter to replenish his brush more frequently with paint. Furthermore, during application of the paint the brush constructed from such bristles is apt to cause streaks and over-application of paint, especially immediately after dipping the brush in paint. If the shiny surface can be properly roughened so as to increase its area, the retention of the bristle is improved. If the size and relative positions of the microscopic indentations or protrusions can be properly controlled, the bristle may be converted from a mediocre bristle to a highly improved and useful adjunct in manufacturing bristles for paint and the like.

As pointed out before, many other uses of a roughened nylon monofilament could be cited but these examples serve as typical instances and are thought to adequately pose the problem. It is within the contemplation of this invention to increase the surface area of the nylon monofilament in a specific controlled manner so as to achieve the desired surface phenomenon without expense to the other desirable characteristics of the line, included among which are its high strength for small diameter filaments and the limpness or flexibility of the material.

It is therefore an important object of the invention to provide a nylon filament and a method for its manufacture in which the surface area and characteristics are improvedfor purposes such as the cited examples without harming or lessening the other desirable attributes of the filament.

It is another object of the invention to provide a monofilament line in which the light reflectivity has been minimized while retaining full strength of the line and improving the flexibility or limpness of the line by the process employed in its treatment.

It is a further object of the invention to provide a roughened nylon filament line and a novel process for treating the filament in which the surface of the filament becomes more retentive of viscous liquids without losing other desirable attributes which make it advantageous for such use as bristles in paint brushes.

It is a still further object of the invention to provide a novel method for treating a filament composed of a nylon formulation wherein the surface of the filament is dipped momentarily in an etching solution to dissolve small quantities of the surface in a microscopically uneven manner and then to redeposit some of the dissolved surface substance in a dull, microscopically granular surface coating which supplements and intensifies the characteristics achieved by the etching step'.

These and other objects and advantages of the invention will more fully appear from the following description made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the several views, and in which:

Fig. 1 diagrammatically sets forth the steps involved in the treatment of my nylon filament;

Fig. 2 is a greatly enlarged segment of untreated monofilament nylon line showing the concentrated light reflecting area characteristic of such line;

Fig. 3 is a greatly enlarged segment of a piece of nylon filament line treated by my process to alter the surface characteristics there of and subjected to light in exactly the same manner as the untreated filament of Fig. 2, the diffusion and dissipation of light rays being evident therefrom; and

Fig. 4 is another greatly enlarged segment of monofilament line treated by my process but after having been drastically rubbed to mechanically remove the re-deposit of nylon coating material, the initial pitting and etching still remaining and serving partially to dissipate light rays 3 and increasing partially the viscous liquid-retentive powers of the filament.

Referring to the drawing, the diagrammatic illustration of the treating process is set forth in Fig. 1. A large spool 10 containing a quantity of nylon monofilament ll is positioned for unwinding in alignment with a series of containers 12, 13 and 14 which are adapted to contain respectively a quantity of etching fluid 15, a plain water bath 16 and a neutralizing solution 17. Rollers or other means of changing the direction of the filament 11 may be employed in a variety of positions to cause the traveling filament to bend downwardly and dip into the various solutions. These elements are shown at 18 for container 12, at 19 for container 13, and 20 for container 14. The filament 11 is threaded upon the guide means as shown, and the treated material on the continuous length of filament is designated at 21 beyond the last of the containers 14 at which position the treated filament is dried and wound upon a collecting spool 22.

In a specific example in the treatment of my monofilament nylon line, I employ nylon monofilament having a diameter of .014 inch. A control length of untreated filament was removed from the spool before the remainder was processed. The filament 11 was then run through an etching bath consisting of 90 percent formic acid for an immersed distance of between 4-5 inches as signified by the length of arrow 23 in Fig. 1, after which the filament traveled in the air before entering the water 16 in container 13 for a length of approximately 6-8 inches and designated by arrow 24 in Fig. 1. The line 11 was run at a speed of approximately 25,000 feet per hour. The treated nylon together with the untreated control length was then dipped in boiling water and the material was placed in a drying oven where it was held at 155 F. for approximately 10 hours, following which both the treated and untreated material were air-dried for a further 24 hours. untreated filament appeared to have the same size, showing that the diameter of the filament had not been reduced but merely changed with respect to the surface characteristics by the process. I have successfully employed [formic acid of from 80 to 90 percent in strength and have subjected nylon lines to such acid for periods ranging from .01 up to 1.0 seconds for each increment thereof. The treated and untreated filaments were then tested for breaking strength and the following results were obtained in a sequence of tests:

Untreated Treated Plain Nylon, Nylon, pounds pounds were consecutively tested on a Tinus Olsen stiffness tester, and the samples under a 10 percent load caused a needle deflection as follows:

Untreated Treated material, material, degrees degrees Average Average The flexibility or limpness of the treated material thus shows to be approximately, 20 percent improved over the untreated nylon without sacrificing strength as indicated above.

Although the exact physical phenomenon resulting from my treatment is not fully known or understood by me, it appears that an etching solution of a fairly strong acid is requisite. The acid should not be of too Weak a type or dilution, and should not be too strong and corrosive. For example, when employing the equivalent process with glacial acetic acid, the results were so unsatisfactory as to be nil. On the other hand, concentrated nitric acid and sulphuric acid reacted so rapidly and was Both the treated and so diflicult to control that the use thereof was abandoned. The formic acid, however, in the neighborhood of the strength noted, proved ideal and further could be relied on to continue its solvent action with controlled pitting and etching during the split second after coming out of the etching fluid and prior to rinsing in the water bath. Other acid baths successfully employed by me were hydrochloric acid of approximately 12 to 20 percent concentration, concentrated sulphuric acid diluted down approximately to one part of acid per 3 parts of water, percent phosphoric acid diluted to 2 parts of acid to one of water, and formic acid ranging from 70 percent to full strength (approximately percent). It is my theory that the film of etching solution clinging to the filament as it emerges from the etching bath continues to dissolve some of-the surface of the filament with lessening intensity but becoming more and more saturated with dissolved nylon. The nylon solution, upon hitting the water bath 16, immediately precipitates a granular or flaky coating which becomes firmly bonded to the previously etched core and coats the entire surface, including the intervening areas between pits or microscopic any possible acid which might be present on the line.

I have successfully employed a single rinsing and neutralizing bath in which the filament proceeds directly from the acid bath and air suspension into a single mild neutralizing bath where the precipitation occurs simultaneously with neutralization of any acid remaining on the line.

Microscopic examination of segments of treated and untreated monofilament lines which are otherwise identical in chemical composition and original diameter, is

illustrated in Figs. 2, 3 and 4. Fig. 2 shows a microscopic view of an untreated length 25 of nylon monofilament. Light was cast from the same source and incident rays were concentrated in a reflective line or band signified by the light medial area 26, the area 27 to either side being practically devoid of reflective power. The shiny and glazed untreated monofilament thus will characteristically reflect light in a pronounced and eye-catching manner. This same line, because of its sleekness, will not easily retain viscous fluids such as paint.

Fig. 3 shows the nylon monofilament after having been treated according to my process. At the surface of this treated segment were observed etched areas 28 randomly disposed over the surface of the core 2 of the filament segment. Annularly superimposed over the entire surface including that of the microscopic indentations or pits 28, is a coating of granular precipitated nylon 30 which presents a grain substantially finer than that of the relatively coarse pits or indentations 28. I believe that this coating 30 constitutes flakes or grains of nylon which were previously dissolved for a split second and then precipitated when the filament struck the water bath. It will be noted that when the filament is exposed to light rays of exactly the same angle and under the same conditions as the untreated filament, the light is so diffused and dissipated as to form no band area at all but merely to be reflected evenly from all portions of the coated area. That this coating is a separate entity seems to be provable by drastic rubbing of such filament as illustrated in Fig. 3 until the coating has been substantially removed therefrom. The appearance of the treated filament with the outer coating removed is as shown in Fig. 4. The pits or indentations 28 are more pronounced in character and the areas interspersed between the randomly formed pits 28 have regained some of their polished and glossy appearance. The net result, however, is still one of diffusion and dissipation of light rays although a suggestion of polished reflection is seen in the medial longitudinal area indicated at 31. Even after partially removing the precipitated coating, the line has a light reflectivity substantially devoid of glare. The remaining granular coating of precipitated nylon, together with the indented areas 28, still function in a manner to retain viscous liquids to make the filament suitable for paint brushes and the like.

Further experimentation has shovm that the time factor is extremely important in treating my monofilament nylon line. Where the proper physical appearance was attained with acids slightly weaker than those above cited by subjecting the line increment thereto for a period in excess of one second, the strength of the line was notably decreased. 'On the other hand, by employing fairly strong acids of the strength noted and below a concentration which will oxidize or unduly corrode the nylon line and subjecting each increment of the nylon line to the selected acid for a period of time ranging from a few hundredths of a second up to one second, the full strength of the line can be preserved. My discovery is particularly fortunate in that the high rate of speed required to preserve the strength of the line also makes for high production of treated monofilament.

It may thus be seen that I have discovered a method of treating nylon filament and particularly the nylon classed as monoaminomonocarboxylic amide in such a manner as to improve the ability of the filament surface to diffuse and dissipate light rays cast thereon and also to improve viscous liquid retaining powers of the filament without sacrifice of strength and while still retaining the ability to control stiffness and flexibility of the filament.

What is claimed is:

1. The method of treating monofilament nylon line to improve its properties, consisting in the steps of etching and pitting microscopically the surface of the line in a strong solution of formic acid lying in a range of percent to full strength for a period of time ranging from 1.0 to .01 seconds, permitting a film of the formic acid with nylon dissolved therein to remain in contact with said line for a short period of time after said etching time, and redepositing at least some of the dissolved nylon onto the etched surface in a dull coating which, together with the etched and pitted surface, will increase the flexibility of the line without decreasing the tensile strength thereof and will efficiently dissipate reflected light therefrom and better retain viscous liquids when placed in contact therewith.

2. The method of treating monofilament nylon line consisting in the steps of immersing the monofilament line in an acid bath of such strength and for a time not to exceed one second so as to etch the surface of the line microscopically without impairing its tensile strength or reducing the diameter thereof, permitting the film of acid with nylon dissolved therein to remain on the line in the presence of air for a short period of time after the etching time, and then innnersing the line with the film thereon in water to redeposit at least some of the dissolved nylon onto the etched surface in a dull coating which, together with the etched and pitted surface, will increase the flexibility of the line and will efiiciently dissipate reflected light therefrom and better retain viscous liquids when placed in contact therewith.

References Cited in the file of this patent UNITED STATES PATENTS 2,251,508 Watson Aug. 5, 1941 2,507,299 DAlelio et a1. May 9, 1950 2,559,080 MacAllister July 3, 1951 FOREIGN PATENTS 123,630 Australia Apr. 6, 1944 555,490 Great Britain Aug. 25, 1943 568,092 Great Britain Mar. 19, 1945 

1. THE METHOD OF TREATING MONOFILAMENT NYLON LINE TO IMPROVE ITS PROPERTIES, CONSISTING IN THE STEPS OF ETCHING AND PITTING MICROSCOPICALLY THE SURFACE OF THE LINE IN A STRONG SOLUTION OF FORMIC ACID LYING IN A RANGE OF 70 PERCENT TO FULL STRENGTH FOR A PERIOD OF TIME RANGING FROM 1.0 TO .01 SECONDS, PERMITTING A FILM OF THE FORMIC ACID WITH NYLON DISSOLVED THEREIN TO REMAIN IN CONTACT WITH SAID LINE FOR A SHORT PERIOD OF TIME AFTER SAID ETCHING TIME, AND REDEPOSITING AT LEAST SOME OF THE DISSOLVED NYLON ONTO THE ETCHED SURFACE IN A DULL COATING WHICH, TOGETHER WITH THE ETCHED AND PITTED SURFACE, WILL INCREASE THE FLEXIBILITY OF THE LINE WITHOUT DECREASING THE TENSILE STRENGTH THEREOF AND WILL EFFICIENTLY DISSIPATE REFLECTED LIGHT THEREFROM AND BETTER RETAIN VISCOUS LIQUIDS WHEN PLACED IN CONTACT THEREWITH. 